Method of removing one or more of the metals of the iron group from solutions containing salts of one or more of the said metals



March 14, 1933. K w MAER 1.900.996

METHOD OF REMOVING ONE OR MORE OF THE METALS OF THE IRON GROUP FROMSOLUTIONS CONTAINING SALTS OF ONE OR MORE OF THE SAID METALS Filed Aug.12, 1929 Patented Mar. 1 4, 1933 I UNITED STATES PATENT mm xmrr wrnrmnimrun or ,s'rocnno, SWEDEN HEDHOD @F REMOVING ONE OR monitor 'rnn arm orman nor: enonnraont SOLUTIONS CONTAINING SALTS OF ONE OR MORE OF THE8AM) MET a lication filed August 12, 1929,.Serial in.

- The metals of the iron group, e. g. iron and'nickel are soluble inmercury in rather considerah e quantities provided fectly pure surfacesof the said metals freed from oxide films and other covers are broughtinto contact with the mercury.

This circumstance may be utilized in several ways for the extraction ofthe iron group metals from difi'erent materials contion is 0.08 volt.

tainlng said metals.

The present invention relates to a method of removing one or more of themetals of the iron group from solutions containing salts of one or moreof the saidmetals by.

electrolysis with the use of a cathode consisting of mercury whichis'kept in motion and preferably made to flow, and is characterized inthat the mercury is causedto flow at such a rate with regard to thecurrent density that the deposited metal is completely removed by themercury in amalgamated form without appearing as afilm or coating on thecathode surface at the current density used. In the preferred embodimentthe mercury is caused to flow in a vertical or inclined direction so asto present vertical or jnclined active surface.

' The general rule isthat the voltage necessary for precipitatinghydrogen on a mercury cathode from an acid solution of a certain'hdrogen ion concentration is higher than the voltage which is needed forprecipitating one or more of the iron group metals from thecorresponding metal salt solutions of equivalent metal ionconcentration. Assuming that the voltage which is necessary topreciptate hydrogen on platinum from a l-normal acid solution is putdown as zero according to N ernsts suggestion, the following empiricallyascertained constants hold true:

Thevoltage' required for precipitating hydrogen on iron from 'a l-normalacid solu- The voltage necessary for precipitating hydrogen on mercuryfrom a l-normal acid solution is about 0.8 volt.

When precipitating hydrogen from a neuthat perestates, and in SwedenAugust at, me.

tral solution these numbers are increased by U The voltage necessary forone gramme-ion (56 grams) ferro-ions to the litre is 0A3 volt. For aferro-salt S0111? tion containing 0.001: gramme-ion ferro-ions to thelitre the corresponding voltage is 0.52 volt, independent of the cathodematerial. is common to all the metals of the iron roup that the "Voltaor precipitatin hy rogen on. a mercury cathode is consi erably higherthan the voltage required for precipitating the metal in questionOIl-"COIldltlOIl that the solutions are of equivalent Further'thepotential required for precipitating hydrogen on the metals in questionis substantially lower than the potential required for mercury. From asolution containing one or more of the iron group metals practicallyever trace of metal may be removed by electro ysis with the use of amercury cathode without hydrogen being evolved at the cathode insubstantial quantity.

Certain metals, as known, are reduced at the cathode to their lowestdegree ofoxidation by the electrolysis before metal is precipitated.Often it is, vantage to. efl'ect such of a suitable reducing theelectrolysis. I From the above theoretical explanation it will beevident as well, that it is a necessary a reduction by means agentbefore starting condition for suppressing the'evolution of precipitating'IR'OII from a ferro-salt solution containing a which is necessaryprecipitating hydrogen on ct gramme-ion concentrations.

the .afore-said it is evident that in however, of great adcause in sucha case a cathode consisting ofone or more of the iron group metals isobtained, which according to the afore-said will cause an immediateconsiderable increase in the evolution of hydrogen and a correspondingdecrease of the current efliciency with respect to the metal or metals.By usin mercury as cathode material this drawbac is avoided inconsequence of mercury havirg a liquid state of aggregation at normaltemperature and owing to the above-mentioned capability of mercury of amgamated form without appearing as a him or coating on the cathodesurface at the current density used. I

The invention is particularly suitable for the manufacture of iron-freealuminium salts. 0n treating clay or other aluminiumbearing mineralswith acids aluminium as well as considerable quantities of iron aredissolved which latter contaminatethe extracted aluminium salts. Severalmethods of removing iron from these salt solutions have been suggestedwithout, however, solving the problem from a technical-economicalstand-point.

According to the invention lead is preferably used as anode material forthe electrolysis of an aluminium sulphate solution containing iron saltswhich may have been previously reduced in any suitable manner. Said leadanode may, if desired, be surrounded with a suitable diaphragm in orderto revent the falling down of lead su eroXi e. When electrolyzingaluminium c 10- ride solution carbonis preferably used as anodematerial. a

Asset forth in the beginning'of this specification the precipitationpotential of hydrogen increases with decreasing acidity. From this factit may be easily concluded that the electrolytes whether t ey consist ofaluminium salt solutions or other solutions, should be kept as nearlyneutral as. ossible in order to secure a good current e ciency. Beforethe electrolysis one ma therefore, if desired, decrease the acidity othe solutions by the addition of suitable neutralizing agents such etc.By the addition of Ca-CO the acidit in a. solution of aluminium sulphatew 'c is acid due to hydrolysis may be reduced to about 0.0001-normal.- T

A suitable device for carrying out the process according to theinvention. is described in the following withreference to the attacheddrawing in which Fi .1 is a side elevation and Fig. 2 a planof ninstallation according to the-invention. The electrolysis takes place inthe, cell 1- which comprises a number 'of cathodes consisting of mercuryflowing over suitable bearers or supports, as well as a correspondingnumber of anodes. The cathodes and anodes are connected to the currentconductors 2 which are, in their turn, connected to a suitable currentgenerator. V and A oil through as for instance CaCOa H a.-

limp,

state by the flowing cathode mercury.

The power portion of the electrolytic cell is connected with one end ofa U-tube 6, the

other end of which opens out into a vessel 7.

The contaminated cathode mercury flows 0d through this U-tube. .The;level, on which one shank of the tube 6 is joined to the vessel 7 istaken so that the column of mercury of the cient, according to the lawoi? communicating vessels, to counter-balance the column of electrolyteof the height a-l-b in the cell 1. Hence no electrolyte will flow 0dtogether with mercury through the tube 6 and the whole quantity ofelectrolyte may be drawn process has been completed.

From the vessel 7 the mercury flows through a pipe 9 to a centrifugalpump 10 driven by an electromoter 11, which pump raises the mercury tothe purifying vessel 12. The mercury is continuously supplied to saidvessel 12 by the pump. In the vessel 12 the contaminated mercury issubjected to the actionof a suitable agent or means for removing metaltaken up by said mercury.

From the vessel 12 the purified mercury flows back through a pipe 13 tothe electro-. lytic cell where it is caused to flow along the bearers orsupports acting as cathode.

The following experiment was made:

A quantity: of 100 cm: aluminium sulphate solution, containin about 100gr. aluminium and 3.45 gr. iron mainly as bivalent iron) to the litre,said solution having been previously reduced and neutralized by theadditio of .100 gr. CaCO to. the litre, was electr 'yzed for 50 minuteswith the useof a flowing mercury cathode. age was 6.2 volts, thecurrent-stren h 0.60 the cathode surface 20 cm, t us the current density3 amp. to the square decimeter. At the end of the experiment the ironpercentage had'fallen to 0.048 gr. to the litre, i. e., the ironpercentage had been de-:

creased from-3.45% to 0.48% calculated on the quantity of A1 0,contained in the solution. The current efiiciency became thus (3.45-0.048) x 0.1 x 9e500 1oo 50 45.1% zsxaeoox xac deposited metals beingheight I) in tube this sufithe cock 8 after the electrolyzing Theaverage voltlbs wards be removed from: the mercury continually and/orintermittently so that said mercury may circulate in the process asextracting, respectively cathodematerial, For such reasons the mercuryis freed from dis solved metal for instance by treating with a solutionof mercurous nitrate or in any other suitable way, and is thenreconveyed to the process.

The above embodiment has only been cited by way of example, as themethod according to the invention may be varied in many ways within thelimits of the claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates of erica is:

1. In a rocess for removing one or more metals of the iron group fromsolutions containing salts of such metals by electrolysis with a cathodeconsisting of continuously flowing mercury, the improvement whichcomprises causing the mercury to flow at such a rate with regard to thecurrent density that the deposited metal is completely removed by themercury in amalgamated form without appearing as a film or coating onthe cathode surfaceat the current density used.

2. In a process for removing one or more metals of the iron group fromsolutions con-- taining salts of such metals by electrolysis with acathode consisting of mercury continuously flowing in a vertical orinclined:

direction so as to present a vertical or inclined active surface, theimprovement which comprises causing the mercury to flow at such a ratewith regard to the current density that the deposited metal iscompletely removed by the mercury in amalgamated form without appearingas a film or coating on tihe cathode surface at the current density useIn testimony whereof I aflix m signature.

KNUT WILHELM PAMAER

